LIBRARY OF CONGRESS. 






rMTEI) STATES OP AMERICA. 



Primers 



of 



Forestry 



/ 








Edwin J. Houston, A. M. 



Professor of Physical Geography and Natural Philosophy, Central 
High School, Philadelphia. Professor of Physics, Franklin 
Institute of Pennsylvania. Member of the Penn- 
sylvania Forestry Association, etc. 



PHII,ADE1.PHIA 



JI. 



.^<:? 



Copyrighted by 
PROF. EDWIN J. HOUSTON, 

1891. 



J-' 



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Primers of Forestry. 

NO. I. — DRAINAGE. 

The rain that falls on the earth either runs 
directly off the surface or sinks into the ground. 

The part that runs directh- off the surface col- 
lects in small streams that discharge into a river, 
which finally discharges into some other river, 
into a lake, or directly into the ocean. 

The part which sinks into the ground collects in 
pockets or places under the surface called reser- 
voirs, from which, as a rule, it comes out at the 
surface at some lower level, as a spring. The flow 
of water in a river, dining most of the time, is 
kept up by these springs pouring their waters 
into the many streams that emptA- into the river 
channel. 

The water, therefore, that falls from the sky as 
rain flows directh* from the earth's surface into a 
river, or it first collects in a reser\-oir. from which 
it afterwards flows into the river. 

The running of the water from the higher level 
of the place where the rain fell to a lower level, 
is called drainage. 

There are two kinds of drainage : 

(i) Surface drainage, or where the rain water 
runs directly off the surface. 

(2) Underground drainage, or where the rain 
Avater first sinks into the groimd and then dis- 
charges into some stream that empties into a river. 

Surface drainage takes place rapidly, and occurs 
mainly during the time rain is falling. It practi- 
calh- stops generally a few hours after the rain 
ceases. 



Underground drainage takes place slowly and 
may continue for many weeks after the rain 
ceases. 

All the water in a river comes from the rain 
that falls on the earth's surface. The river con- 
tinues to flow because before all the water drains 
from the earth into the river, more rain falls and 
keeps up the supply. 

Some rivers are larger than others. This is 
because — 

(i) More rain falls on those parts of the earth 
through which they flow, and 

(2) The land which slopes towards such riv^ers 
covers a greater part of the earth's surface. 

The water runs off the earth from a higher to a 
lower level, because water runs down hill. The 
direction in which water will drain from the land 
will depend on the direction of the .slope of the 
land. 

If the land slopes so that all the water that 
drains from it collects in streams that flow into 
the ocean through a common river mouth, and 
the rainfall on such an area is large, the river it- 
.self will be large. 

The smaller streams and rivers which collect in 
a single and larger river, and di.scharge their 
waters through a common mouth, are called 
collectiveh^ a river system. 

The area of land that drains into a river is 
called a river basin. 

The size of a river, therefore, depends upon the 
amount of the rain-fall on its basin, and on the 
size of its ba.sin. 

When the quantity of water discharged into a 
river is greater than its channel can hold, a flood 
occurs, or the river is said to inundate its banks. 

A heavy rainfall does not necessarily produce 

4 



an inundation ; since if the character of the river 
basin is such that a comparatively small part shall 
run directly off the surface, and a large part 
shall sink into the ground, collect in the reser- 
voirs of springs, and slowh' pass through such 
springs into the rivers, sufficient time may be 
given for the river to discharge the waters of 
even a very heavy rainfall. 

If, however, the character of the surface is such 
that the larger part of the rainfall runs dipctly 
off the slopes into the river channel, then an inun- 
dation must necessarily attend every heavy rain- 
fall. 

Whenever the greater part of the rainfall runs 
directly off the surface into the rivers, and a com- 
paratively small part goes to feed the reserv^oirs 
of springs, if a comparatively long time elapses 
before the next rainfall, the springs will dr>' up, 
and the water in the river will get very low. 

Any disturbance in the natural drainage of a 
country may cause a damage of two different kinds. 

(i ) The damage due to the overflowing of the 
rivers, or that due directly to too much water. 

(2) The damage due to the dr^dng up, or the 
getting low of the rivers, in the intervals between 
the storms, or that due to too little water. 

The portion of the rainfall that sinks quietly 
into the earth as compared with that which flows 
directly' from its surface depends on the character 
of the surface. As a rule, a surface devoid of 
vegetable covering, that is a surface on which no 
plants or other vegetation are growing, will per- 
mit a larger part of the rainfall to drain directly 
into the river channels than will a surface cov- 
ered by vegetation. This is especially the case 
during the colder parts of the year, when the 
ground is frozen. 



When the rain falls on a surface covered bj- 
vegetation, the water, by slowly trickling down 
the stalks or stems of the leaves, branches and 
trunks of the trees, finds a ready entrance into the 
ground by following their surfaces and discharg- 
ing into the porous ground lying outside their 
roots. 

A forest, that is a section of ground covered by 
trees, permits this action to take place quite 
read^y. 

A forest, therefore, tends to decrease the fre- 
quency of floods, because it decreases the amount 
of the rainfall that drains directly from the earth's 
surface. 

A forest also tends to prevent the occurrence of 
too little water in a river, because it ensures the 
filling of the reservoirs of springs, which discharge 
their waters into the rivers in the intervals between 
the rainfalls. 

The forests must therefore be preserved in order 
that the rivers may properl3^ aid in draining the 
earth. 



Primers of Forestry. 

NO. 2. — RAIN. 

When rain falls on the earth, it either, for the 
greater part, runs directly off the surface, or sinks- 
into the ground. 

A part, however, passes upward into the air in 
the form of invisible water or vapor. 

If a plate filled with water be exposed to the 
air on a warm day the water will at last entirely 
disappear. In a similar manner wet clothes, 
when hung out in the air, become drj^ because 
all the water they contain passes off into the 
atmosphere as invisible water or vapor. 

When water disappears in this way, that is, 
when visible water turns into invisible vapor, the 
process is called evaporation. 

The amount of invisible water or vapor which 
a given quantit}^ of air can hold depends on the 
warmth or coldness of the air. The hotter the 
air, the greater is the amount of invisible water or 
vapor it can contain. 

When moist air is heated it acquires the power 
of holding a greater amount of water in an inx'isi- 
ble state than it formerly did, and therefore be- 
comes drier. 

When moist air is cooled the quantity of invisi- 
ble water it can hold becomes smaller, and, if the 
cooling is carried sufficiently far, some of this in- 
visible water becomes visible as rain, dew, fog or 
cloud. 

When, therefore,air containing moisture is suffi- 
ciently cooled, the moisture it can no longer hold 



falls as rain. The amount of the rain which falls 
depends not only on the quantity of air that is 
chilled, but also on the extent of this chilling and 
the quantity of moisture the air contained before 
it was chilled. 

The lowering of temperature necessary to pro- 
duce rain may be caused in the following ways : 

(i ) The moist air may blow along the earth's 
surface towards colder regions. 

(2) The moist air ma\- rise directly from the 
earth's surface into the higher and colder regions 
of the air. 

As a rule, the moist air which blows along the 
earth's surface towards the poles becomes chilled 
and deposits its moisture as rain, or snow. On 
the contrary, for the greater part, the moist air, 
which blows along the earth's surface towards the 
equator, becomes warmer, and, thus becoming 
drier, takes rather than gives moisture, and pro- 
duces drought. 

Therefore, as a rule, only the surface winds 
which blow towards the colder regions of the 
earth can be expected to bring rain. 

Mountains form excellent means for cooling the 
air, and causing its invisible water or vapor to 
fall as rain. They act, no matter in what direc- 
tion the wind may be blowing. 

When a wind blows again.st the side or slopes of 
a mountain, it is forced by the pressure of the wind 
back of it to slowly creep up the slopes of the 
mountain, where it becomes chilled in the 
colder regions which lie near the summit of the 
mountain. If this lowering of temperature be 
sufficiently great, the moisture will be precipi- 
tated from the air, no matter from what direction 
the wind ma\- come. 



Mountains ma}- therefore cause rain to fall from 
any wind that is forced to blow over them, pro- 
vided they are sufficiently high to cause the neces- 
sary amount of cooling. When a mountain 
reaches sufficiently upward into the air, or is high 
enough to make the temperature fall below the 
freezing point of water, the moisture falls as snow. 

The reason so many rivers rise in mountains is 
to be found in the fact that they act to chill the 
winds, and so rob the air of its moisture, no mat- 
ter in from what direction the wind, which is 
forced to ascend their slopes, may happen to blow. 

The sources of nearly all the rivers of the world 
are found in mountainous districts. As a rule, 
the largest rivers of the world rise in the highest 
mountains. This is because the higher the 
mountain the colder its slopes ; the cold mountain 
slopes acting, as explained, to deprive the air 
of its moisture. 

The rain that falls on a mountain's slopes, like 
that which falls on any other part of the earth's 
surface, either runs directly off the surface, or 
sinks into the ground. 

The part which runs directly off the surface 
will be greater than the part which sinks into the 
ground when the surface is bare and devoid of 
vegetation. On the contrary, the part which 
sinks into the ground will be greater than the 
part which runs directly off the surface, when the 
surface is covered with forests. But where the 
sides of a mountain are covered with forests, 
the part of the rainfall which sinks into the 
ground, as compared with that which runs 
directly off the surface, is greater than in any 
other case. 

Since the rivers]_which rise in the mountains 



are more regularly fed by the springs when 
the greater part of the rainfall sinks quietly into 
the ground, and since this occurs on mountains 
that are covered with trees, the importance of 
keeping the sides of the mountains wooded is 
evident. 

When the sides of mountains are covered 
with forests the rivers that rise on their slopes are 
both less apt to overflow their banks during heavy 
rainfalls and also less apt to dry up and become 
shallow during droughts, than if such forests are 
removed. 

The forests should, therefore, be preserved on 
the mountain sides, in order to protect the low 
lands either from inundations or floods, or from 
the effects of too small a quantity of water in 
the rivers which flow throuarh them. 



Primers of Forestry. 

NO. 3. — CONDITIONS NECESSARY FOR THE 
GROWTH OF PLANTS. 

The following conditions are necessary for the 
growth of plants : 

(i) The germ or. seed from which the plant 
grows. 

The germ or seed in all cases comes directly 
from a plant exactly similar to that which will 
be produced when the seed sprouts or germinates. 

(2) The cradle where the plant is born. 

The plant's cradle is the soil. In this soil the 
plant spreads its roots, and from it, obtains, in 
greater part, the materials necessary for its nour- 
ishment and growth. 

(3) The sunshine, as well as the heatshine, 
which awaken the sleeping germ and call it into 
activity ; or, in other words, the light and heat, 
which are so essential to a plant's life and growth. 

(4) The nourishment, or the food which the plant 
takes into its structure and so causes it to become 
a part of itself. 

The process by which a plant takes different 
materials from the soil in which it grows or from 
the air around it, and causes them to become a 
part of its structure, is called a.ssimilation. At 
the commencement of its life the plant gets its 
nourishment from materials in the seed surround- 
ing that part of the seed which is called the germ. 
Soon, however, the plant gets its nourishment from 
the soil and the atmosphere ; or, in other words, 
from outside the seed. 

This latter nouri.shment of the plant comes from 
various materials, the most important of which are : 

(i) Moisture. 

This moisture is taken up mainly by the roots 



of the plant, but is sometimes absorbed directly 
by the leaves. 

(2) Carbonic acid. 

Carbonic acid is a gaseous substance formed of 
carbon or charcoal combined with an invisible gas 
called oxygen. The carbonic acid is absorbed by 
the leaves of the plant, and, in the presence of 
sunshine, is broken up into carbon and oxygen. 
The oxygen is given off from the surface, and the 
carbon is kept bj- the plant to form its woody 
fibre. In the case of large vegetable forms like 
forest trees, the amount of carbonic acid that is 
taken from the air and con^'erted into woody fibre 
must be very great. 

(3) Mineral matters taken from the soil. 

A plant contains various kinds of mineral sub- 
stances which are taken directly from the soil. For 
the proper growth of the plant the soil in which it 
grows must contain the particular mineral sub- 
stances which naturally exist in its structure. 
In addition to this, the soil must contain .such 
mineral substances in a condition or state in 
which they can be readily taken up by the plant. 

The conditions necessary for plant growth : 
viz., the germ, the cradle, the sun's light and 
heat, and some form of solid and liquid food, are 
not equally necessary for the growth of a plant. 

The presence of the germ or seed is, of course, 
of the greatest importance, since without it 
no plant can grow. 

The sunshine and the heat may possibly be 
considered as next in importance to the growth 
of the plant. Heat and light are to be found in 
practically all parts of the earth. They differ, 
however, in amount, and such differences cause 
the differences that are noticed in the plants that 
grow in different regions of the earth. 



The nourishment of the plant conies next in 
order of importance. The quantity of carbonic 
acid found in the air is practically the same in all 
parts of the earth. The quantity of moisture 
found in the air differs very greatly in different 
parts of the earth, and on this difference, together 
with the difference in temperature, depends the dif- 
ference observed in the plants of various regions. 

The soil is, perhaps, the least important of the 
conditions required for plant growth. 

Where a particular kind of plant is to be raised, 
the character of the soil probably stands next in 
importance to the presence of the germ or seed ; 
for, each plant thrives best in a particular kind of 
soil. The variety of plants that exist are, how- 
ever, so great that, given almost any kind of soil, 
together with the other conditions of heat, light 
and moisture, that soil will be found to be the 
soil best suited to the growth of some particular 
kind of plant. In other words, if the proper con- 
ditions of moisture, heat and light are present, 
and the gerni is present, vegetation will appear 
in almost any region of the earth. 

Nature has generously scattered the germs of va- 
rious forms of plant-life all over nearly the earth's 
surface ; and, if unmolested by man, will maintain 
on such surfaces the kind of plant-forms or plant 
growths best suited to grow naturally. 

There will, therefore, be found in every section 
of country a plant-growth, or plant-life, that is 
peculiar to, or that naturally belongs to such a 
section of country. Each section of country pos- 
sesses, so to speak, a nationality in its plant- 
growth ; or, in other words, there lives in each 
section of country a particular nation of plants. 
Such a nation of plants, or such plants as are pecu- 
liar to each section of the country, is called its flora. 

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Sincejieat, light and moisture are, next to the 
presence of the plant-germ, the most important 
things for plant growth, there will necessarily 
exist a difference in the flora of different parts of 
the earth according to the differences that exist 
in the distribution of heat, light and moisture 
over the earth's surface. 

The heat, light and moisture that exist at the 
Equator are greater in amount than at any other 
portion of the earth's surface. Therefore, the 
vegetation at the tropics is more luxuriant and 
possesses a greater diversit}- of forms than at 
any other part of the surface. As we pass from 
the Equator towards the poles the decrease in the 
heat, light and moisture causes a similar decrease 
in the variety and luxuriance of vegetation. 

In passing from the base to the summit of a 
high tropicalinountain, the same differences in the 
variety and luxuriance of plant life will be noticed 
that are seen in going from the Equator to the 
poles. This is due mainly to the differences in 
the distribution of the heat and moisture. 

The planting of a germ or seed, therefore, in 
any soil, will not result in its continual growth, 
unless the conditions of heat, light and mois- 
ture are practically the same as those in which 
the plant from which such germ or seed was 
derived required for its existence. 

Trees planted in a particular locality may, 
therefore, fail to grow in such locality from want of 
the proper conditions of heat, light and moLsture. 
Consequently, trees, that are so important to the 
proper flow of rivers, should be carefully pre- 
served in all those localities where they can grow 
naturally ; for, in such places, they will grow the 
best. When it is necessary to cut down forests, 
they should, wherever practicable, be replanted. 

14 



Primers of Forestry. 

NO. 4. — CONDITIONS NECESSARY FOR THE 
GROWTH OF TREES. 

If a .soil exist in any locality, and certain con- 
ditions of light, heat and moisture are present, 
the character of the vegetation that naturally 
grows in such a region will depend more on 
the peculiarities of the distribution of the heat, 
light and moisture, than on the character of the 
soil itself 

If the moisture be entirely absent, or if it 
exists in such a form, as for example as ice or 
snow, in which it can not be readily appropriated 
by the plants, then that region becomes a desert. 

Deserts occur either in dry, arid regions, or in 
the cold regions that exist on the higher moun- 
tain slopes amid the regions of perpetual snow. 

If the moisture is absent during certain months 
of the year, and a rainfall occurs during the other 
months, that is, if one part of the year is dry and 
the rest is wet, the vegetable forms, which die or 
disappear during the dry season, reappear during 
the wet season. Portions of the earth that have 
this character of vegetation are called steppe 
regions. 

When the moisture does not fall as rain in very 
great amounts, but is fairly well distributed 
throughout the year, regions occur which are 
called prairies or meadows. 

If there is an abundance of moisture at nearly 
all times throughout the year, and, for no very 
long time is such moisture absent, then the coun- 
ts 



try ma}^ be covered by trees, and form what are 
called forest regions. 

Forests cannot exist in the temperate zones of 
the earth in localities where, during the time of 
the trees' growth, a very long interval exists dur- 
ing which no rain falls. While the growth of the 
tree is suspended, as during the winter, this ne- 
cessity for liquid nourishment of course no longer 
exists. 

The reason forests cannot grow except where 
moisture is present nearl}^ all the time the plants 
are growing will be easily understood from the 
following considerations : 

Suppose a soil exists in any section of countr}% 
and suppose such soil contains plant germs of 
practically all varieties : then, when such a soil 
is submitted to the action of light, heat and 
moisture, these germs will be called into active 
life, and various forms of plant life will begin 
their existence. 

Suppose this particular section to be a region 
where for several months of the j^ear no rain falls. 
On the appearance of such a dr}?- season all forms 
of plant life will disappear or die from w'ant of 
proper nourishment. 

On the reappearance of the wet season only 
those forms of plant life that have been able, dur- 
ing the brief time of the wet season, to reach 
their full growth and to produce their fruit or 
seeds, will be able to supply the germs neces- 
sary for a new growth. Such forms as trees, 
which, as is well known, require many years to 
mature their fruit or seed, will neces.sarily be 
unable to grow naturally in such a region of 
country. 

Of course, it might easily happen that during 
the first wet season all the germs might not have 
i6 



been called into active life by the eombined 
influence of the light and heat, so that on the 
next wet season such forms might spring up 
naturally. But their continued existence, under 
such circumstances, would be impossible from the 
absence of the new germs necessary to produce 
such plants. 

Only those plants, therefore, can grow in a sec- 
tion of country where the rainfall is limited to 
certain periods of the year, that, during the time 
the rain continues and water is supplied to them, 
can reach their maturity and develop their seeds, 
so that they may be capable of reproducing the 
germ, and therefore be ready for the appearance 
of the next rainy season. 

For the growth of forests, a certain depth of 
soil and, in general, a certain character of soil is 
necessary. This soil may have been, in greater 
part, the result of prior generations of plants, 
and, in the beginning, forests could not grow in 
localities even where the proper conditions of light, 
heat and moisture are present, until such soil has 
been prepared for them. 

Extensive forests, therefore, can exist naturall}' 
only in such regions where the rainfall during 
their time of growth is maintained with a certain 
approach towards regularitj- ; that is where trees 
are properly and continually supplied with their 
liquid nourishment. 

It is mainly in the temperate regions of the 
earth that the great forest districts are to be 
found, since it is mainly in these regions that the 
rain may fall at almost any time of day and on 
almost an}' day of the year. 

There are, however, extensive forest districts 
in parts of the tropical regions where the rainfall 
may occur at certain times during the day 

17 



throughout nearly all the days of the year, even 
though the rest of the year is dry. 

It is especially on the sides of mountains, 
where rain may fall in no matter from what direc- 
tion the wind comes, that forests are to be found in 
nearly all portions of the earth's surface, pro- 
vided the heat is sufficiently great, and a suit- 
able soil is present. These conditions exist on 
nearly all mountain slopes outside of the polar 
regions. 

The mountains may, therefore, be regarded as 
the natural home of the forests. The moun- 
tains are also the natural places where the ri\'- 
ers begin. The preservation of the forests on 
the sides of mountains is necessary for such 
a drainage of the rainfall as will best preserve the 
uniform flow of the rivers and will best prevent 
the rivers from overflowing their banks in times of 
rain, or becoming too shallow in times of drought. 

The forests should be preserved and maintained 
on the sides of mountains. When it is necessary 
to cut down the forests for the sake of the timber 
they furnish, the trees should, in all cases, be re- 
planted, so that forests shall not disappear from 
the face of the earth. 



Primers of Forestry. 

NO. 5. — THE DESTRUCTION OF THE FOREST.S. 

When the forests are removed from any con- 
siderable section of country, disturbances are pro- 
duced not only in the climate of that section, but 
also to a marked extent in the character of the 
distribution of its rainfall, and, to a more limited 
extent, in the amount of its rainfall. 

The removal of the forests from any considerable 
section of country is, in the end, invariably at- 
tended by the following results : 

(i) An increase in the frequency with which 
the rivers of that section of country inundate or 
overflow their banks. 

(2) An increase in the frequency and severitj- 
of droughts as witnessed by a marked decrease in 
the amount of water in the river channel, and in_ 
the frequency with which the springs, in such 
section of countr}^ either show a marked de- 
crease in their flow, or drj^ up altogether. 

(3) A marked disturbance in the lower course 
of the river, produced by the filling up of its 
channel by sand bars or mud flats. 

(4) A decrease in the healthfulness of the dis- 
tricts that border the lower course of the river ; 
that is, in those portions of the river which lie in 
the lowlands near the river's mouth, or where the 
river empties into the sea. 

When the forests are removed from any section 
of country the rain that formerly drained that 
section, mainly by gradually sinking into 

19 



the porous ground, by running along the 
branches and trunks of the trees and so enter- 
ing and penetrating the ground to comparatively 
great depths, now drains rapidly off the surface. 
The rainfall, instead of reaching the river channel 
quietly and slowly through a discharge from the 
reservoirs of springs, now rapidly drains directly 
off the surface into the river channel. 

Instead of reaching the river channel in, say a 
period of three weeks, the rain water drains into 
the channel in often a period of as many hours. 
The river channel is therefore overcharged with 
water ; the river overflows its banks, and the 
floods, so caused, carry loss to the low lands along 
the river banks, and often death to the inhabi- 
tants. 

Not only are the riches of the rainfall thus 
squandered to the loss of the people living in the 
river valleys from the excess of water immediately 
after a rainfall, but a still greater and far more 
reaching loss occurs from the failure of the rain- 
fall to fill the reservoirs of springs, the continuous 
discharge of which is necessary to maintain the 
proper flow of water in the river. 

The damage, however, does not stop here. The 
rapid drainage of the surface carries off and dis- 
charges into the river channel the soil in which 
the forest grew ; for, this soil, being now no 
longer held together by the roots of the trees and 
the underbrush of the forest is rapidly carried 
away by the water. The soil thus carried away 
resulted from the continued growth of former 
generations of plants and probably required cen- 
turies for its production. Its loss in a few years 
is, therefore, a very serious matter. 

The soil, the wealth of the highlands, is 
now thrown into the river channel, and 



though it may for the time fertilize the lowlands, 
through inundations by the river, yet it often, 
for the greater part, collects in sand bars and 
mud flats on the lower courses of the once navi- 
gable rivers which formed the natural waterways 
of intercommunication. 

These mud flats work injury, 

(i) By hindering navigation and thus interfer- 
ing with the commerce between different parts 
of the country. 

(2) By becoming sources of contamination to 
the air of the lowlands by breeding weakening 
and other fatal miasmatic diseases. 

The axe of the pioneer, so often regarded as 
the emblem of civilization, is, perhaps, more cor- 
rectly to be regarded as the emblem of an entirely 
different character. 

The solution of the problem of the preservation 
and protection of the forest is one of extreme 
difficulty for the following reasons : 

The parts of the earth where the highest 
civilization exists, or which form the natural 
home of civilized man, were originally covered 
by trees. Civilized man cannot continue, as a 
dweller in the forest. The dense popula- 
tions which now exist in most of the temperate 
regions of the earth could not continue to exist 
in the forest regions which once covered them. 

There are, however, regions where forests can 
and should be maintained by the strictest provi- 
sions of law, and these are to be found on the 
slopes of mountain ranges, which form the natural 
places where rivers rise. 

Forests should be preserved on the slopes of 
those mountain ranges in which the important 
rivers of a country take their origin for the follow- 
ing purposes : 

21 



(i) For the proper distribution of the rain 
which falls on such mountains. 

(2.) For the purpose of keeping constant the 
rate of drainage of the rainfall. 

(3) For the purpose of protecting the naviga- 
ble rivers which have their origin on such moun- 
tain slopes. 

(4) For the purpose of decreasing the area of 
the malarial districts at the mouths of such rivers. 

(5) For the purpose of preventing the loss of 
that soil which required so many generations of 
plants to produce. 

Let laws therefore be enacted providing for the 
replanting of trees on such mountain slopes, 
either when they have been removed by the axe 
of the woodman, or by fire. 





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